Inflator

ABSTRACT

The present invention provides an inflator which is easily connected to an air bag.  
     Stud bolts  51, 52  are fixed by welding to the side faces of a first closure  30  and a second closure  40 , which are connected to a cylindrical housing  20 . When connecting a gas introduction port of the air bag to a diffuser portion  43 , the stud bolts  51, 52  do not cause an obstruction, and hence the attachability of an inflator  10  to a module case using the stud bolts  51, 52  is not impaired.

FIELD OF THE INVENTION

The present invention relates to an inflator for use in an air bag system of an automobile.

RELATED ART

An inflator used in an air bag system of an automobile is attached to a vehicle body using a different attachment method depending on the type and structure of the inflator. In the case of a front passenger side inflator comprising an elongated housing, the inflator itself is incorporated into a module case, and hence a method of fixing the inflator to the module case by bolting a stud bolt provided on the end surface of the housing is applied principally.

However, some side air bag inflators and curtain air bag inflators for use in lateral collisions are attached to the air bag by connecting a gas discharge hole of the inflator directly to a gas introduction port of the air bag. In the case of this type of inflator, if the stud bolt is provided on the end surface, the stud bolt interferes with the air bag, and hence connecting the inflator to the air bag becomes difficult. As a method of solving such problems, JP-B No. 2528596 and JP-B No. 3133267 disclose inflators comprising a stud bolt on the side surface of the housing.

DISCLOSURE OF THE INVENTION

The inflators in JP-B No. 2528596 and JP-B No. 3133267 are both provided with a separate outside housing surrounding the housing, to which stud bolts are attached. As a result, the overall size of the inflator increases, and hence these inflators are not suitable as a side air bag inflator or curtain air bag inflator having a particularly restricted attachment space.

An object of the present invention is to provide an inflator which is capable of responding sufficiently to demands for reduced size and weight, and with which the attachment work of an inflator having restricted attachment space, such as a side air bag inflator or curtain air bag inflator, can be performed easily.

As means for achieving these objects, the present invention provides an inflator comprising a cylindrical housing, both ends of which are open, a first closure attached to an opening portion on one end of the cylindrical housing, and a second closure attached to an opening portion on the other end of the cylindrical housing, wherein

-   -   a pressurized gas is charged into a sealed space surrounded by         the cylindrical housing, the first closure and the second         closure,     -   an ignition means is accommodated inside the first closure, and         a gas discharge hole is provided in the second closure, and     -   a stud bolt is fixed directly to at least one of a side face of         the first closure and a side face of the second closure by         welding.

By fixing a stud bolt directly to one or both of the side face of the first closure and the side face of the second closure by welding in this manner, the size and weight of the inflator can be reduced below those of the inflators disclosed in JP-B No. 2528596 and JP-B No. 3133267. There are no particular limitations on the method of fixing and welding the stud bolt, but resistance welding is preferably applied.

Further, by welding the stud bolts to the side face of the first closure and the side face of the second closure, the penetration depth of the welding portion is increased, thereby increasing the fixing strength.

Note that the cylindrical housing, first closure and second closure are also fixed together by welding. This welding operation may be performed before or after the stud bolts are fixed to the first closure and second closure.

In the inflator described above, both the side face of the first closure and the side face of the second closure, which contact the stud bolts during the welding, are preferably flat surfaces.

By forming a flat surface portion on part of the side faces of the first closure and second closure, and forming the end face of the stud bolts to be attached to the flat surface portions in a protruding form, heat is more likely to accumulate during the resistance welding, thereby preferably increasing the welding strength. The protruding portion on the end face of the stud bolt may be constituted in a hemispherical form, a pointed form, or an annular form, and a plurality of the protruding portions may be formed.

In the inflator described above, the end face of the stud bolts and the side faces of the first closure and second closure, which contact each other during the welding, are preferably formed such that the end face of the stud bolt takes a protruding form or a recessed form, and the side faces of the first closure and second closure take a recessed form or a protruding form which matches the protruding form or recessed form of the end face of the stud bolt.

By correlating the form of the side faces of the first closure and second closure with the form of the end face of the stud bolts in this manner, positioning is easy when welding is to be performed. Note that further providing a small protrusion on the tip end of the protruding portion is useful for resistance welding.

As a result, positioning of the welding locations is easy, the welding (preferably resistance welding) itself is easy, and since no gaps appear, the welding strength can be increased.

Instead of correlating the protruding portion and recessed portion as described above, one, two, or more protruding portions may be provided on the end face of the stud bolt, and a flat surface portion may be formed on part of the side faces of the first closure and second closure so that welding (preferably resistance welding) is performed between the protruding portion and flat surface portion. Conversely, the end face of the stud bolt may be formed as a flat surface, and one, two, or more protruding portions may be provided on part of the side faces of the first closure and second closure so that welding (preferably resistance welding) is performed between the flat surface and the protruding portion.

As another means for achieving the aforementioned objects, the present invention provides an inflator comprising a cylindrical housing having a sealed space into which a pressurized gas is charged and a gas outlet on one end face thereof for releasing the pressurized gas, and an ignition means for opening the sealed space in the cylindrical housing and discharging the pressurized gas through the gas outlet, wherein

-   -   a stud bolt is fixed by welding directly to at least one         location on part of a side face of the cylindrical housing         having a constant thickness.

By fixing a stud bolt directly to the side face of the cylindrical housing by welding in this manner, the size and weight of the inflator can be reduced below those of the inflators disclosed in JP-B No. 2528596 and JP-B No. 3133267. Resistance welding is preferably employed as the method of welding the stud bolts.

Further, when two stud bolts are fixed by welding to the part of the side face of the cylindrical housing having a constant thickness, the welding strength of the two stud bolts can be made identical if welding is performed under identical conditions. In so doing, a situation in which the welding strength of one of the stud bolts decreases does not arise.

In the inflator described above, the side face of the cylindrical housing, which contacts the stud bolt during the welding, is preferably a flat surface.

By forming a flat surface portion on part of the side face of the cylindrical housing, and forming the end face of the stud bolt to be attached to the flat surface portion in a protruding form, heat is more likely to accumulate during the resistance welding, which is preferable. The protruding portion on the end face of the stud bolt may be constituted in a hemispherical form, a pointed form, or an annular form, and a plurality of the protruding portions may be formed.

In the inflator described above, the side face of the cylindrical housing, which contacts the stud bolt during the welding, is preferably a curved surface, and the end face of the stud bolt is preferably provided with a protruding portion.

Resistance welding can also be applied when the stud bolt is welded to a curved surface as described above. In this case, if one, two, or more protruding portions are formed on the end face of the stud bolt, the protruding portions melt during the resistance welding, the melt moves into the gap between the curved surface and the stud bolt, and thus the curved surface of the cylindrical housing and the stud bolt are fused. Hence the amount by which the protruding portion protrudes is determined in consideration of the magnitude of the gap. When two or more protruding portions are provided, the lengths thereof are adjusted to fit the curvature of the side face of the cylindrical housing.

The inflator of the present invention may be applied to a well-known inflator, and is particularly suitable as a curtain air bag inflator or side air bag inflator. The inflator of the present invention may also be applied to a driver side inflator, a front passenger side inflator, or a knee bolster inflator.

The inflator of the present invention does not use a separate member such as the outside housing of JP-B No. 2528596 and JP-B No. 3133267 when the stud bolts are fixed, and is able therefore to respond adequately to demands for reduced size and weight. Moreover, the number of manufacturing steps is reduced, thereby improving productivity.

The inflator of the present invention excels particularly in facilitating the attachment work of an inflator having restricted attachment space, such as a side air bag inflator or curtain air bag inflator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an inflator of the present invention in the axial direction thereof.

FIG. 2 is an illustrative view of a stud bolt attachment method according to another embodiment.

FIG. 3 is a sectional view of another embodiment of the inflator of the present invention in the axial direction thereof.

FIG. 4 is a sectional view of another embodiment of the inflator of the present invention in the axial direction thereof.

DESCRIPTION OF REFERENCE NUMERALS

10 inflator 20 cylindrical housing 22 pressurized gas chamber 24 first rupturable plate 28 second rupturable plate 30 first closure 34 igniter 36 gas generating agent 40 second closure 42 gas discharge hole

Preferred Embodiments of the Present Invention (1) First Embodiment

FIG. 1 is a sectional view of an inflator in the axial direction thereof, and FIGS. 2(a) through 2(d) are illustrative views of a stud bolt attachment method.

An inflator 10 comprises a cylindrical housing 20, both ends of which are open, a first closure 30 attached to an opening portion on one end of the cylindrical housing 20, and a second closure 40 attached to an opening portion on the other end of the cylindrical housing 20.

A pressurized gas such as argon, helium, or nitrogen, serving as an air bag inflation medium, is charged into a sealed space (pressurized gas chamber) 22 surrounded by the cylindrical housing 20, first closure 30 and second closure 40. The charging pressure is set at a maximum pressure of approximately 70,000 kPa.

The cylindrical housing 20 is made of steel or the like having a peripheral wall of a constant thickness. The cross-sectional form thereof is not limited to a circular form, and may be polygonal or elliptical.

The interior of the first closure 30 forms an ignition means chamber 32 accommodating an electric igniter 34 and a required amount of a gas generating agent 36. The igniter 34 is fixed by crimping an opening end edge 37 of the first closure 30. The ignition means chamber 32 is at normal pressure.

The first closure 30 (ignition means chamber 32) and the pressurized gas chamber 22 are connected by a communication path 39 which is closed by a first rupturable plate 24 prior to an activation of the inflator. The first rupturable plate 24 is fixed to an end portion wall of the first closure 30 by welding.

A cap 25 including plural vent holes 26 is provided to cover the communication path 39 from the pressurized gas chamber 22 side. A flange portion 27 at a peripheral edge of the cap 25 is fixed by crimping with a peripheral edge 38 of the end portion in the first closure 30.

The second closure 40 is provided with plural gas discharge holes 42. A gas introduction port of the air bag is connected to a diffuser portion 43 in which the gas discharge holes 42 are provided. An interior space 44 of the second closure 40 is at normal pressure.

The second closure 40 (interior space 44) and the pressurized gas chamber 22 are closed from each other by a second rupturable plate 28. The second rupturable plate 28 is fixed to a flange portion 45 of the second closure 40 by welding.

A stud bolt 51 is fixed to a side face of the first closure 30 by resistance welding, and a stud bolt 52 is fixed to a side face (the flange portion 45) of the second closure 40 by resistance welding. The thickness of the respective welding locations is considerably greater than the thickness of the peripheral wall of the cylindrical housing 20. The stud bolts 51, 52 are positioned colinearly in the axial direction of the inflator 10, and fixed to extend in a perpendicular direction to the axial direction.

The side faces of the first closure 30 and second closure 40, which contact the stud bolts 51, 52 respectively during welding, are both flat. Note, however, that the side faces of the first closure 30 and second closure 40 may be curved, and the stud bolts 51, 52 may be welded to the curved surface portions thereof.

As shown in FIG. 2(a), a side face 55 of the first closure 30 (or second closure 40), which contacts the stud bolt 51 (or 52) during welding, may be provided in a protruding form, and an end face 53 of the corresponding stud bolt 51 (or 52) may be provided in a recessed form, such that the resistance welding is performed between the protruding form and recessed form.

Conversely, as shown in FIG. 2(b), the side face 55 of the first closure 30 (or second closure 40), which contacts the stud bolt 51 (or 52) during welding, may be provided in a recessed form, and the end face 53 of the corresponding stud bolt 51 (or 52) may be provided in a protruding form. In this case, a further protrusion is preferably provided on either the protruding part or recessed part so that heat can be generated on the protruding part more easily during the resistance welding.

As shown in FIG. 2(c), plural protruding portions 57 may be provided on the end face 53 of the stud bolt 51 (or 52) and the side face 55 of the corresponding first closure 30 (or second closure 40) may be provided as a flat surface portion, such that the resistance welding is performed between the protruding portions 57 and the flat surface portion. The protruding portions 57 may be plural independent protruding portions or an annular protruding portion.

Note that the side face of the first closure 30 (or second closure 40) may be formed as a curved surface, and the plural protruding portions 57 may be formed on the end face 53 of the stud bolt 51 (or 52) in a form which matches the form of the curved surface.

As shown in FIG. 2(d), the end face 53 of the stud bolt 51 (or 52) may be formed as a flat surface, and the side face 55 of the corresponding first closure 30 (or second closure 40) may be provided with a protruding portion 58, such that the resistance welding is performed between the end face 53 and the protruding portion 58. The protruding portion 58 may take the form of a plurality of independent protruding portions, or may be an annular protruding portion.

By correlating the form of the end face 53 of the stud bolt 51 (or 52) and the form of the side face 55 of the corresponding first closure 30 (or second closure 40) as shown in FIGS. 2(a) to 2(d), positioning of the welding locations can be performed easily, welding itself can be performed easily, and the welding strength can be increased.

When resistance welding is applied as the welding method, a method of pressing together the end face 53 of the stud bolt 51 (or 52) and the side face 55 of the corresponding first closure 30 (or second closure 40), and causing a large current to flow between the two may be employed. The two components may also be fixed using arc spot welding. Welding may be performed using similar methods in the other embodiments to be described below.

Next, an operation performed when the inflator 10 (applied as a curtain air bag inflator or a side air bag inflator) shown in FIG. 1 is incorporated into an air bag system installed in an automobile will be described.

Note that the inflator 10 is attached within a prescribed module case by a combination of the stud bolts 51, 52 and nuts, and that the gas introduction port of the air bag is connected to the diffuser portion 43. At this time, the stud bolts 51, 52 are fixed to the side face of the inflator 10, and therefore do not interfere with the air bag that is connected to the inflator 10 in the axial direction thereof. As a result, the operation to connect the diffuser portion 43 and the gas introduction port of the air bag can be performed easily, and the attachability of the inflator 10 to the module case by the stud bolts 51, 52 is also favorable.

When the vehicle crashes and receives a shock, operation signal outputting means cause the igniter 34 to activate, whereby the gas generating agent 36 is ignited and burned so as to generate high temperature combustion gas. The high temperature combustion gas causes the internal pressure of the ignition means chamber 32 to rise, as a result of which the first rupturable plate 24 ruptures, releasing the combustion gas into a cap 25. The combustion gas is then ejected through a vent hole 26 into the pressurized gas chamber 22, causing the internal pressure of the pressurized gas chamber 22 to rise. The pieces of the first rupturable plate 24 are trapped by the cap 25. As a result of the increase in pressure in the pressurized gas chamber 22, the second rupturable plate 28 ruptures, whereby the pressurized gas and combustion gas pass through the internal space 44 and are discharged from the gas discharge holes 42. Thus the air bag is inflated.

The air bag is inflated in the axial direction of the inflator 10, but since the stud bolts 51, 52 are fixed to the side face of the inflator 10 (in an orthogonal direction to the axial direction), they do not obstruct the inflation of the air bag in the axial direction.

(2) Second Embodiment

FIG. 3 is a sectional view of an inflator in the axial direction thereof. The inflator shown in FIG. 3 differs from the inflator 10 shown in FIG. 1 only in the fixing positions of the stud bolts 51, 52.

The stud bolts 51, 52 are fixed to the peripheral wall (having a constant thickness) of the cylindrical housing 20 by resistance welding. The stud bolts 51, 52 are positioned colinearly in the axial direction of the inflator 10, and are fixed to extend in a perpendicular direction to the axial direction.

The stud bolts 51, 52 and the peripheral wall of the cylindrical housing 20, which contact each other during welding, preferably have a similar relationship to one of those shown in FIGS. 2(a) to 2(d) from the point of view of increasing the welding strength. Otherwise, these components may take a similar form to that described in the first embodiment.

The peripheral wall of the cylindrical housing 20 has a constant thickness, and therefore when the two stud bolts are welded, the welding strength of the two stud bolts can be made equal by performing welding under identical conditions. In so doing, workability is favorable, and a situation in which the welding strength of one of the stud bolts is weaker than that of the other stud bolt does not arise.

(3) Third Embodiment

FIG. 4 is a sectional view of an inflator (inflator 100) in the axial direction thereof, and also serves as an illustrative view of an air bag attachment method.

A cylindrical housing 112 has an opening portion 114 at one end side thereof, whereas the other end side thereof is closed. An inert gas such as argon or helium, a nitrogen gas, or similar is charged into a sealed space (pressurized gas chamber) 116 at a maximum pressure of approximately 70,000 kPa. The cylindrical housing 112 has a circular cross section in the axial direction, and the opening portion 114 has a similar circular form.

Stud bolts 151, 152 are fixed to the peripheral wall (having a constant thickness) of the cylindrical housing 112 by resistance welding. The stud bolts 151, 152 are positioned colinearly in the axial direction of the inflator 100, and fixed to extend in a perpendicular direction to the axial direction.

In order to increase the welding strength, the stud bolts 151, 152 and the peripheral wall of the cylindrical housing 112, which contact each other during the welding, preferably have a similar relationship to one of those shown in FIGS. 2(a) to 2(d), and particularly to that shown in FIG. 2(c). Otherwise, these components may take a similar form to that described in the first embodiment.

A diffuser portion 120 is connected to the opening portion 114 side of the cylindrical housing 112. The diffuser portion 120 has a first gas discharge hole 122 serving as a gas outlet through which the pressurized gas is released to the outside. The cylindrical housing 112 and diffuser portion 120 may be connected by welding or by being screwed together.

A pressurized gas outflow path 118 (serving as a gas outlet) between the opening portion 114 (serving as a gas outlet) of the cylindrical housing 112 and the diffuser portion 120 is closed by a rupturable plate 119, and a sealed space 116 of the cylindrical housing 112 is maintained in a high-pressure airtight state prior to an activation. In FIG. 4, the rupturable plate 119 is attached in the diffuser portion 120 side, but may be attached in the opening portion 114 side of the inflator 112. The first gas discharge hole 122 of the diffuser portion 120, on the other hand, is not closed.

An igniter 126 comprising a priming is provided in the diffuser portion 120 as rupturing means for rupturing the rupturable plate 119 (opening means for opening the sealed space 116). The igniter 126 is attached after connecting the cylindrical housing 112 to the diffuser portion 120 by being inserted toward the rupturable plate from an opening portion on one end of the diffuser portion 120. Following its insertion, the igniter 126 is fixed by crimping a peripheral edge 128 of the opening portion on the one end of the diffuser portion 120. 130 denotes a connector insertion space.

A gas discharge port 140 communicates the diffuser portion 120. These two components are connected by pressing and inserting a pressurized gas inflow portion 142 of the gas discharge port 140 into the first gas discharge hole 122 of the diffuser portion 120. At this time, the diameter of the inflow portion 142 of the gas discharge port 140 is set to be slightly smaller than the diameter of the first gas discharge hole 122 of the diffuser portion 120.

One end of the gas discharge port 140 is closed (closed end face 162), and the other end is open. The gas discharge port 140 comprises a main body portion 140 a including a flange portion 163, and an adapter portion 140 b. These components are connected by meshing or fitting the flange portion 163 of the main body portion 140 a into the interior of the adapter portion 140 b, and then crimping the end portion of the adapter 140 b, but may also be connected by resistance welding. Note that the main body portion 140 a and adapter portion 140 b of the gas discharge port 140 may also be formed integrally.

The adapter portion 140 b and diffuser portion 120 are connected by resistance welding at a welding portion 135. Here, the adapter portion 140 b (inflow portion 142) and diffuser portion 120 may be resistance welded, and then the main body portion 140 a connected thereto, or the adapter portion 140 b and diffuser portion 120 may be resistance welded after connecting the main body portion 140 a to the adapter portion 140 b.

Plural opening portions (second gas discharge holes) 160 is provided in the side face of the main body portion 140 a, and a screen 148 comprising plural outflow holes 149 for removing foreign objects from the pressurized gas which passes therethrough is disposed in the interior of the main body portion 140 a. The hole diameter of the outflow holes 149 may be selected from the numerical value range of between 0.5 and 2.0 mm.

At least two of the plural opening portions 160 are disposed in symmetrical or almost symmetrical positions in the widthwise direction. Six opening portions 160, for example, may be provided at equal intervals in the circumferential direction.

The screen 148 may be constituted by one or plural laminated layers of punching metal, plain weave wire gauze, or a similar material, formed into a cylindrical form and disposed such that the axial direction of the screen 148 and the axial direction of the gas discharge port 140 (main body portion 140 a) are in alignment. The outflow holes 149 are provided over the entire surface of the screen 148, but substantially only those that face the opening portions 160 discharge the pressurized gas and thus exhibit a foreign object removal action.

A protruding portion 164 and a groove portion (recessed portion) 161 are provided consecutively or at an interval (preferably consecutively) in the circumferential direction on the side of the main body portion 140 a near the adapter 140 b.

The protruding portion 164 has a flat top face which may be provided with a screw portion (male screw portion or female screw portion) if necessary, and is provided in the vicinity of the opening portions 160. The protruding portion 164 is used when connecting the inflator 100 to the air bag at the gas discharge port 140. The radial direction height and axial direction length of the protruding portion 164 may be determined in consideration of the connectability (connecting strength, workability, etc.) with the air bag.

The groove portion 161 is used when assembling the air bag device to tighten the gas introduction port of the air bag onto the main body portion 140 a after placing the gas introduction port on to the main body portion 140 a. As a result, the two components can be joined securely, preventing the air bag from falling. The depth of the groove portion 161 in the radial direction may be determined in consideration of the connectability (connecting strength, workability, etc.) with the air bag.

In the inflator 100, the stud bolts 151, 152 are fixed to the side face of the inflator 100, and therefore do not obstruct the air bag, which is connected in the axial direction of the inflator 100. As a result, the operation to connect the gas discharge port 140 and the gas introduction port of the air bag can be performed easily, and the attachability of the inflator 100 to the module case of the inflator 100 is also favorable. Moreover, since the air bag inflates in the axial direction of the inflator 100, the stud bolts 151, 152 do not obstruct the inflation of the air bag.

As well as the inflator 100 shown in FIG. 4, one, two, or more stud bolts may also be welded to the peripheral wall of an inflator illustrated in FIGS. 1 to 6 of JP-A 2003-104164 in a similar manner to this embodiment, whereby similar actions and effects are obtained. 

1. An inflator comprising a cylindrical housing, both ends of which are open, a first closure attached to an opening portion on one end of the cylindrical housing, and a second closure attached to an opening portion on the other end of the cylindrical housing, wherein a pressurized gas is charged into a sealed space surrounded by the cylindrical housing, the first closure and the second closure, ignition means are accommodated inside the first closure, and a gas discharge hole is provided in the second closure, and a stud bolt is fixed directly to at least one of a side face of the first closure and a side face of the second closure by welding.
 2. The inflator according to claim 1, wherein both the side face of the first closure and the side face of the second closure, which contact the stud bolt during the welding, are flat surfaces.
 3. The inflator according to claim 1, wherein an end face of the stud bolt and the side faces of the first closure and second closure, which contact each other during the welding, are formed such that the end face of the stud bolt takes a protruding form or a recessed form, and the side faces of the first closure and second closure take a recessed form or a protruding form which matches the protruding form or recessed form of the end face of the stud bolt.
 4. An inflator comprising: a cylindrical housing having a sealed space into which a pressurized gas is charged and a gas outlet on one end face thereof for releasing the pressurized gas; and ignition means for opening the sealed space in the cylindrical housing and discharging the pressurized gas through the gas outlet, wherein a stud bolt is fixed by welding directly to at least one location on part of a side face of the cylindrical housing having a constant thickness.
 5. The inflator according to claim 4, wherein the side face of the cylindrical housing, which contacts the stud bolt during the welding, is a flat surface.
 6. The inflator according to claim 4, wherein the side face of the cylindrical housing, which contacts the stud bolt during the welding, is a curved surface, and an end face of the stud bolt is provided with a protruding portion.
 7. The inflator according to claim 1 or 4, serving as a curtain air bag inflator or a side air bag inflator. 